NASA Moon Probe Celebrates 4th Birthday on Supermoon Sunday

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A sharp-eyed NASA spacecraft celebrates four years of circling
the moon this Sunday (June 23), just in time for the "supermoon."

Since arriving in orbit on June 23, 2009, NASA's
Lunar Reconnaissance Orbiter (LRO) has given scientists a
much deeper understanding of Earth's nearest neighbor, mission
team members said.

"Not only has LRO delivered all the information that is needed
for future human and robotic explorers, but it has also revealed
that the moon is a more complex and dynamic world than we had
ever expected," Rich Vondrak, LRO deputy project scientist at
NASA’s Goddard Space Flight Center in Greenbelt, Md., said in a
statement. [ Celebrating
LRO's Fourth Anniversary (Video) ]

Appropriately enough, LRO marks its fourth anniversary on the
same day that the biggest and brightest full moon of 2013 — the
so-called " supermoon "
— lights up Earth's night sky.

The moon's path around Earth is slightly elliptical; distances
between the two bodies vary from 225,622 miles (363,104
kilometers) at the closest lunar approach, known as perigee, to
252,088 miles (405,696 km) at apogee. Supermoons result when the
full moon and perigee coincide.

The $504 million LRO spacecraft is about the size of a Mini
Cooper car and sports seven different science instruments. It
zips around
the moon at an altitude of 31 miles (50 km).

LRO launched on June 18, 2009, along with a piggyback probe
called the Lunar Crater Observation and Sensing Satellite. In
October 2009, LRO watched from orbit as LCROSS and the duo's
Centaur booster rocket slammed deliberately into a shadowed
crater at the moon's south pole, blasting out surprisingly large
amounts of water ice.

Data from the probe's laser altimeter helped mission scientists
build the best map of lunar surface altitude variations ever
constructed, and LRO's Cosmic Ray Telescope for the Effects of
Radiation instrument (CRaTER) measured the radiation environment
around the moon.

"In its four years in orbit, LRO has revealed a new moon with
discoveries that address the moon's history and by extension the
Earth's history as well," John Keller, LRO project scientist at
NASA Goddard, said in a statement.

"The innovative measurements by LRO have answered many questions
asked by planetary scientists, but have also uncovered new
questions as well," Keller added. "I'm looking forward to future
work on these new questions as LRO continues to study the moon."

To date, LRO has completed nearly 18,000 orbits, traveling about
125 million miles (200 million km) around the moon in the
process, researchers said. It's slated to continue operating
until October 2014, though a two-year mission extension is a
possibility.